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Amino acid concentration (nmol/g of muscle) in leg muscle of obese rats 

Amino acid concentration (nmol/g of muscle) in leg muscle of obese rats 

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To determine how the ability of skeletal muscle to manage amino acids is conditioned by obesity. The test was performed in two different models of obese rats: diet-obese rats and genetically obese rats. Lean and genetically obese (fa/fa) male Zucker rats were used. For up to 60 d of life lean animals were fed with standard chow pellet or with a hyp...

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... the genetically obese group showed a lower protein content than lean and diet-obese groups ( Table 1). The concentrations of free amino acids in the whole leg muscle are shown in Table 2. In diet-obese animals there was a signi®cant increase only in Ser concentration compared with the other groups. ...

Citations

... Until recently, there was very little evidence on protein metabolism in skeletal muscle of humans with obesity, despite original evidence collected in rodents decades ago showing that obesity is linked to adverse effects on protein metabolism in muscle (Durschlag and Layman, 1983;Lanza-Jacoby and Kaplan, 1984;Friedman et al., 1990;Herrero et al., 1997). Early efforts to understand protein metabolism in humans with obesity focused on whole-body protein turnover, but subsequent studies provided original evidence for impaired protein turnover occurring specifically in muscle of these individuals (Guillet et al., 2011;Katsanos and Mandarino, 2011). ...
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Studies investigating the proteome of skeletal muscle present clear evidence that protein metabolism is altered in muscle of humans with obesity. Moreover, muscle quality (i.e., strength per unit of muscle mass) appears lower in humans with obesity. However, relevant evidence to date describing the protein turnover, a process that determines content and quality of protein, in muscle of humans with obesity is quite inconsistent. This is due, at least in part, to heterogeneity in protein turnover in skeletal muscle of humans with obesity. Although not always evident at the mixed-muscle protein level, the rate of synthesis is generally lower in myofibrillar and mitochondrial proteins in muscle of humans with obesity. Moreover, alterations in the synthesis of protein in muscle of humans with obesity are manifested more readily under conditions that stimulate protein synthesis in muscle, including the fed state, increased plasma amino acid availability to muscle, and exercise. Current evidence supports various biological mechanisms explaining impairments in protein synthesis in muscle of humans with obesity, but this evidence is rather limited and needs to be reproduced under more defined experimental conditions. Expanding our current knowledge with direct measurements of protein breakdown in muscle, and more importantly of protein turnover on a protein by protein basis, will enhance our understanding of how obesity modifies the proteome (content and quality) in muscle of humans with obesity.
... For example, increased blood concentration of specific amino acids and their metabolites is associated with obesity and type 2 diabetes mellitus (T2DM) (Adams, 2011;Adibi, 1968;Felig et al., 1969). While BCAAs are predictive biomarkers for T2D risk (Batch et al., 2013;Newgard, 2009Newgard, , 2012Wang et al., 2011), their origin is debatable (Herman et al., 2010;Herrero et al., 1997;Zhao et al., 2016). Our data support a scenario where increased circulating amino acids mostly reflect increased skeletal muscle protein turnover (Figures 6A and S3). ...
Article
Metabolic diseases are often characterized by circadian misalignment in different tissues, yet how altered coordination and communication among tissue clocks relate to specific pathogenic mechanisms remains largely unknown. Applying an integrated systems biology approach, we performed 24-hr metabolomics profiling of eight mouse tissues simultaneously. We present a temporal and spatial atlas of circadian metabolism in the context of systemic energy balance and under chronic nutrient stress (high-fat diet [HFD]). Comparative analysis reveals how the repertoires of tissue metabolism are linked and gated to specific temporal windows and how this highly specialized communication and coherence among tissue clocks is rewired by nutrient challenge. Overall, we illustrate how dynamic metabolic relationships can be reconstructed across time and space and how integration of circadian metabolomics data from multiple tissues can improve our understanding of health and disease.
... After one moth of treatment, control animals weighted 370 ± 15 g and those in the cafeteria-fed group 450 ± 11 g (p < 0.05 vs. controls), these values and those of plasma metabolites were similar to other previously described obtained the same dietary model and handling setup (Herrero et al., 1997). Mean daily metabolizable energy intake of control rats was 7.34 ± 0.36 kJ, rats in the cafeteria group ingested 18.4 ± 0.76 kJ/per day (p < 0.05 vs. controls). ...
... The higher blood flow to striated muscle observed in the cafeteria group is in agreement with a steadier (and increased) supply of substrates to sustain muscle growth and maintenance, coincident with the described increase of amino acid availability (Herrero et al., 1997) and body protein accrual of cafeteria diet-fed rats. ...
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Background. A “cafeteria” diet is a self-selected high-fat diet, providing an excess of energy, which can induce obesity. Excess of lipids in the diet hampers glucose utilization eliciting insulin resistance, which, further limits amino acid oxidation for energy. Methods. Male Wistar rats were exposed for a month to “cafeteria” diet. Rats were cannulated and fluorescent microspheres were used to determine blood flow. Results. Exposure to the cafeteria diet did not change cardiac output, but there was a marked shift in organ irrigation. Skin blood flow decreased to compensate increases in lungs and heart. Blood flow through adipose tissue tended to increase in relation to controls, but was considerably increased in brown adipose tissue (on a weight basis). Discussion. The results suggest that the cafeteria diet-induced changes were related to heat transfer and disposal.
... Although we did not measure muscle 247 intracellular amino acid concentrations, plasma concentrations of amino acids, especially the 248 BCAA, reflect the intracellular levels[40]. Others have shown that whole leg muscle leucine 249 concentration in obese rats is >2X that found in lean animals[41]. During exercise there is 250 increased amino acid release from skeletal muscle[42,43]. ...
Article
Purpose: Protein metabolism is altered in obesity, accompanied by elevated plasma amino acids (AA). Previously, we showed that exercise delayed progression to type 2 diabetes in obese ZDF rats with maintenance of β cell function and reduction in hyperglucocorticoidemia. We hypothesized that exercise would correct the abnormalities we found in circulating AA and other indices of skeletal muscle protein metabolism. Methods: Male obese prediabetic ZDF rats (7-10/group) were exercised (swimming) 1 h/day, 5 days/week from ages 6-19 weeks, and compared with age-matched obese sedentary and lean ZDF rats. Results: Food intake and weight gain were unaffected. Protein metabolism was altered in obese rats as evidenced by increased plasma concentrations of essential AA, and increased muscle phosphorylation (ph) of Akt(ser473) (187%), mTOR(ser2448) (140%), eIF4E-binding protein 1 (4E-BP1) (111%), and decreased formation of 4E-BP1*eIF4E complex (75%, 0.01 ≤ p ≤ 0.05 for all measures) in obese relative to lean rats. Exercise attenuated the increase in plasma essential AA concentrations and muscle Akt and mTOR phosphorylation. Exercise did not modify phosphorylation of S6K1, S6, and 4E-BP1, nor the formation of 4E-BP1*eIF4E complex, mRNA levels of ubiquitin or the ubiquitin ligase MAFbx. Positive correlations were observed between ph-Akt and fed circulating branched-chain AA (r = 0.56, p = 0.008), postprandial glucose (r = 0.42, p = 0.04) and glucose AUC during an IPGTT (r = 0.44, p = 0.03). Conclusion: Swimming exercise-induced attenuation of hyperglycemia in ZDF rats is independent of changes in body weight and could result in part from modulation of muscle AKT activation acting via alterations of systemic AA metabolism.
... Overall, utilization of the metabolic profiling approach in the OVX model demonstrates that metabolic disturbances in the OVX animal do not recapitulate the same metabolic profile observed in other rodent models of obesity. Two frequently observed results include an accumulation of LC (25) and an increase in skeletal muscle BCAA levels in both human and animal models of obesity (19). However, the OVX mice do not exhibit this metabolic profile, suggesting that more studies are needed to critically examine the mechanistic role of female sex steroids in the regulation of peripheral metabolism. ...
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Disruptions of ovarian function in women are associated with increased risk of metabolic disease due to dysregulation of peripheral glucose homeostasis in skeletal muscle. Our previous evidence suggests that alterations in skeletal muscle lipid metabolism coupled with altered mitochondrial function may also develop. The objective of this study was to use an integrative metabolic approach to identify potential areas of dysfunction that develop in skeletal muscle from ovariectomized (OVX) female mice compared to age-matched ovary intact adult female mice (SHAM). The OVX mice exhibited significant increases in body weight, visceral and inguinal fat mass compared to SHAM mice. OVX mice also had significant increases in skeletal muscle intramyocellular lipids (IMCL) compared to the SHAM animals, which corresponded to significant increases in the protein content of the fatty acid transporters CD36/FAT and FABPpm. A targeted metabolic profiling approach identified significantly lower levels of specific acyl carnitine species and various amino acids in skeletal muscle from OVX mice compared to the SHAM animals, suggesting a potential dysfunction in lipid and amino acid metabolism, respectively. Basal and maximal mitochondrial oxygen consumption rates were significantly impaired in skeletal muscle fibers from OVX mice compared to SHAM animals. Collectively, these data indicate that loss of ovarian function results in increased IMCL storage that is coupled with alterations in mitochondrial function and changes in the skeletal muscle metabolic profile.
... High-fat feeding in rodents leads to the development of insulin resistance by promoting excessive storage of triglycerides not only in the adipose tissue, but also in the liver and skeletal muscle (38)(39)(40). There also is evidence for increased availability of amino acids in skeletal muscle of high-fat fed rats (41). We recently observed that S6K1 was overactivated in the fat, liver, and muscle of obese animals (26,27) and that deletion of S6K1 in mice protected these animals against diet-induced obesity and the development of insulin resistance (13,27). ...
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S6K1 has emerged as a critical signaling component in the development of insulin resistance through phosphorylation and inhibition of IRS-1 function. This effect can be triggered directly by nutrients such as amino acids or by insulin through a homeostatic negative-feedback loop. However, the role of S6K1 in mediating IRS-1 phosphorylation in a physiological setting of nutrient overload is unresolved. Here we show that S6K1 directly phosphorylates IRS-1 Ser-1101 in vitro in the C-terminal domain of the protein and that mutation of this site largely blocks the ability of amino acids to suppress IRS-1 tyrosine and Akt phosphorylation. Consistent with this finding, phosphorylation of IRS-1 Ser-1101 is increased in the liver of obese db/db and wild-type, but not S6K1 −/−, mice maintained on a high-fat diet and is blocked by siRNA knockdown of S6K1 protein. Finally, infusion of amino acids in humans leads to the concomitant activation of S6K1, phosphorylation of IRS-1 Ser-1101, a reduction in IRS-1 function, and insulin resistance in skeletal muscle. These findings indicate that nutrient- and hormonal-dependent activation of S6K1 causes insulin resistance in mice and humans, in part, by mediating IRS-1 Ser-1101 phosphorylation. • mTOR • nutrient sensing • amino acids • insulin signaling
... Since high ammonium levels in the media, as ammonium chloride, interfered with the classic method for urea determination by urease [11], urea was determined by a colorimetric assay for ureido compounds [12] using antypirine and diacetylmonoxime. Amino acids were determined by HPLC (Amino System, Gilson) using the OPA (orto-phtaldialdehyde) and FMOC (9-fluorenyl methoxy carbonyl chloride) derivatives [13]. Individual amino acids were separated in a Spherisorb ODS-2 column and in a ternary solvent gradient of sodium phosphate/propionic acid/acetonitrile at room temperature. ...
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The metabolic differences in vitro between genetic and dietary obese rats in the uptake of ammonium and amino acids by the liver and their use for ureogenesis have been assayed using hepatocytes isolated from Lean, Obese Zucker (Genetic obese) rats and Dietary obese rats. The hepatocytes of genetic obese animals took up more ammonium and produced higher amounts of urea from ammonium and alanine than those of lean and dietary obese groups (2 and 5 times more respectively). In the lean and dietary obese groups urea synthesis accounted for almost all the nitrogen taken up as ammonium. Thus, dietary and genetic obesity show a widely different handling of nitrogen, and the genetic obese rats need to break down protein to maintain their hepatocyte function.
Article
Diabetes and obesity are the two notorious metabolic disorders in today’s world. Both diabetes and obesity are interlinked with each other and often referred to as “Diabesity.” It is a complex and multi-organ failure disorder. Thus, many researches and tremendous efforts have been made towards prevention, treatment as well as early detection of diabesity. However, and still, there is a large gap in understanding the etiology as well as treatment of diabesity. Various animal models are also used to decipher the mechanism underlying diabesity. Among all the model organism recently Drosophila melanogaster is gaining its importance to study diabetes, obesity and other metabolic disorder. Various experimental methods like histological, biochemical, developmental and behavioral assays are described in this study to detect diabetes as well as obesity in the fly model.
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Pressurized capillary electrochromatography (pCEC) method was developed to analyze metabolites in normal and obesity rat urine with ethyl chloroformate derivatization. The separation was performed on a capillary column (EP-150-30/50-5-C18), and good resolution was obtained with the mobile phase of water (0.01% TFA)−95% acetonitrile (0.01% TFA) using the following gradient: 0–30 min, 0–50 % B; 30–40 min, 50%–75% B. Under the optimized conditions, such as pressure of 13000 kPa, applied voltage of 2 kV, flow rate of 0.08 ml min−1, and room temperature, the contents of metabolites in the urine of normal and obesity rats were obtained. Under the optimum conditions, the correction coefficients were 0.9988–0.9999 in the range of 1.25–500 g l−1. The intra- and inter-day precisions were less than 5%. The average recoveries ranged from 95.9% to 103.2%. The method is simple, sensitive, and accurate for the determination of endogenous metabolites in rat urine sample.
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Obesity may impair protein synthesis rates and cause anabolic resistance to growth factors, hormones, and exercise, ultimately affecting skeletal muscle mass and function. To better understand muscle wasting and anabolic resistance with obesity, we assessed protein 24-h fractional synthesis rates (24-h FSRs) in selected hind-limb muscles of sedentary and resistance-exercised lean and obese Zucker rats. Despite atrophied hind-limb muscles (-28% vs. lean rats), 24-h FSRs of mixed proteins were significantly higher in quadriceps (+18%) and red or white gastrocnemius (+22 or +38%, respectively) of obese animals when compared to lean littermates. Basal synthesis rates of myofibrillar (+8%) and mitochondrial proteins (-1%) in quadriceps were not different between phenotypes, while manufacture of cytosolic proteins (+12%) was moderately elevated in obese cohorts. Western blot analyses revealed a robust activation of p70S6k (+178%) and a lower expression of the endogenous mTOR inhibitor DEPTOR (-28%) in obese rats, collectively suggesting that there is an obesity-induced increase in net protein turnover favoring degradation. Lastly, the protein synthetic response to exercise of mixed (-7%), myofibrillar (+6%), and cytosolic (+7%) quadriceps subfractions was blunted compared to the lean phenotype (+34, +40, and +17%, respectively), indicating a muscle- and subfraction-specific desensitization to the anabolic stimulus of exercise in obese animals.-Nilsson, M. I., Dobson, J. P., Greene, N. P., Wiggs, M. P., Shimkus, K. L., Wudeck, E. V., Davis, A. R., Laureano, M. L., Fluckey, J. D. Abnormal protein turnover and anabolic resistance to exercise in sarcopenic obesity.